1. Field of the Invention
The present invention relates to vacuum gauges and, particularly, to an ionization vacuum gauge.
2. Discussion of Related Art
Ionization vacuum gauges have been used for several years. The conventional ionization vacuum gauge includes a hot filament, an anode electrode surrounding the hot filament, and an ion collector surrounding the anode electrode. The anode electrode and the ion collector are coaxial relative to the hot filament. In operation, electrons emit from the hot filament, travel toward and through the anode electrode and eventually are collected by the anode electrode. As the electrons travel, they collide with the molecules and atoms of gas and produce ions, and eventually the ions are collected by the ion collector. The pressure of the vacuum system can be calculated by the formula P=(1/k)(Iion/Ielectron), wherein k is a constant with the unit of 1/torr and is characteristic of a particular gauge geometry and electrical parameters, Iion is a current of the ion collector, and Ielectron is a current of the anode electrode.
However, the hot filament of the conventional ionization vacuum gauge is generally a hot tungsten filament. In operation, the tungsten filament requires several watts of electrical power to operate, and dissipates a great deal of heat and light in the vacuum system, and consequently the power consumption of the conventional ionization vacuum gauge is high. Furthermore, the high temperature of the hot tungsten filament can cause evaporation, and thus is not conducive to the vacuum system.
What is needed, therefore, is an ionization vacuum gauge with low power consumption and low evaporation effect.